The application of ultraviolet irradiation (UV) for degradation of guar gum (GG) has been investigated with intensification using addition of hydrogen peroxide (H2O2) and potassium persulfate (KPS). Effect of UV power intensity and initiator concentration on the extent of degradation has been established. The efficacy of UV based approach has been compared with ultrasound (US) and ozone (O-3) based processes on the basis of kinetic rate constant, final limiting viscosity and required treatment time. The combined approaches such as US + UV, US + O-3 and UV + O-3 have also been investigated. For the approach based on UV irradiation, addition of H2O2 and KPS increased the extent of degradation significantly. The combined approaches of US + O-3 and UV + O-3 have been found efficient as compared to individual approaches. Use of UV + H2O2 (0.1% loading) resulted in about 99.1% degradation in 20 min whereas UV + KPS (0.1% loading), US + O-3 (100 mg/h) and UV + O-3 (100 mg/h) resulted in about 98.3%, 99.1% and 98.3% reduction in intrinsic viscosity in 90 min, 30 min and 35 min respectively. In scale-up studies (7 L capacity), maximum extent of degradation as 98.2% was achieved in 150 min using US bath + UV + H2O2 (0.03% loading). The structure of the treated guar gum by all approaches was also characterized by FTIR and it was established that no significant chemical structure changes were obtained due to the treatment. (C) 2015 Elsevier B.V. All rights reserved.